The present invention relates to an electronic apparatus having a voltage converting circuit for converting the voltage of power supplied by an electricity supply device and operated by power outputted from this voltage converting circuit.
FIG. 12 typically shows the schematic construction of a conventional electronic apparatus. As shown in FIG. 12, the conventional electronic apparatus is constructed by a voltage converting circuit 702, a control circuit 105 and a load circuit 104. The voltage converting circuit 702 outputs fourth power 109 by converting the voltage of first power 106 supplied from an electricity supply device 101. The control circuit 105 detects the voltage of second power and outputs a control signal 710 to control an operation of the voltage converting circuit 702 such that the fourth power 109 has a predetermined desirable voltage. The load circuit 104 is operated by the fourth power 109.
In the conventional electronic apparatus having the above construction, the control circuit 105 must be operated in an output voltage control mode having a large consumed electric current but a high control speed at any time so as to follow a variation of a consumed electric current of the load circuit 104. Therefore, when there is a period in which there is almost no variation of the consumed electric current in the load circuit 104, the control circuit 105 is operated in the output voltage control mode although no high control speed is required. Therefore, in this case, a problem exists in that the conversion from the first power 106 to the fourth power greatly becomes worse, and no first power 106 from the electricity supply device 101 can be effectively utilized to operate the load circuit 104.
Further, the voltage converting circuit 702 is limited in a power range able to efficiently output the fourth power 109 from the first power 106. Therefore, in the case of a circuit in which consumed power of the load circuit 104 is extremely changed, there is a case in which power outside the power range able to efficiently output power by the voltage converting circuit 702 is supplied to the load circuit 104. In this case, a problem exists in that no first power 106 from the electricity supply device 101 can be effectively utilized to operate the load circuit 104.
Such a problem is caused particularly when the load circuit 104 is an IC having an operating mode having a large consumed electric current and a violent variation of the consumed electric current, and a standby mode having a small consumed electric current and a small variation of the consumed electric current, and is an IC for a portable telephone having a receiving-transmitting mode having a large consumed electric current and a violent variation of the consumed electric current, and a waiting mode having a small consumed electric current and a small variation of the consumed electric current. The number of cases adopting the IC of such a type in the load circuit 104 is recently increased, and the number of cases causing the above problem is increased in recent years.
The above problem becomes particularly serious in a compact portable apparatus having the same construction as the conventional electronic apparatus of the construction shown in FIG. 12. This is because a battery or a secondary battery as the electricity supply device is made compact and is reduced in capacity as the portable apparatus is made compact and light in weight, but the load circuit consumes high power to raise functions and is difficult to perform an operation for a long time and cannot be further operated for a long time when the above problem is caused.
Further, in a recent compact portable apparatus, it is necessary to make the secondary battery as the electricity supply device compact and light in weight and increase capacity of the secondary battery so as to make the portable apparatus compact and light in weight and raise performance of the portable apparatus and operate the portable apparatus for a long time. Therefore, the type of a high battery voltage tends to be adopted in the secondary battery. In contrast to this, the load circuit of the compact portable apparatus tends to adopt an IC constructed by a MOSFET of a fine structure at the sacrifice of a withstand voltage with respect to the voltage of the load circuit, and a MOSFET having a fine and SOI structure at the sacrifice of a withstand voltage with respect to the voltage of the load circuit so as to reconcile high performance and low consumed power. Therefore, in a recent compact portable apparatus, no load circuit can be directly operated by power of the battery or the secondary battery. Accordingly, similar to the construction of the conventional electronic apparatus shown in FIG. 12, the compact portable apparatus increasingly has a construction in which the power of a high voltage of the secondary battery is converted to power of a low voltage by the voltage converting circuit, and the load circuit is operated by this converted power of a low voltage. Accordingly, the above problem becomes serious in the recent compact portable apparatus.
Further, in the recent compact portable apparatus, the load circuit also tends to adopt an IC having a large difference in the consumed electric current and the consumed electric current variation such as the operating mode and the standby mode, or the receiving-transmitting mode and the waiting mode, etc. to improve performance and reduce power consumption. Therefore, the above problem becomes more serious.
Therefore, a main object of the present invention is to provide an electronic apparatus in which a load circuit having an operating mode extremely different in a consumed electric current and a consumed electric current variation can be efficiently operated by converted power from the electricity supply device.
In a first construction of an electronic apparatus in the invention, the electronic apparatus comprises electricity supply device for supplying power; a voltage converting circuit for converting the power to converted power different in voltage from the power and outputting the converted power; a control circuit for controlling an operation of the voltage converting circuit such that the converted power becomes predetermined desirable power; and a load circuit operated by the converted power; wherein the control circuit has a first output voltage control mode and a second output voltage control mode having a consumed electric current smaller than that in the first output voltage control mode; the load circuit has a first operating mode and a second operating mode having a variation of the consumed electric current smaller than that in the first operating mode; and the electronic apparatus has a period for operating the control circuit in the second output voltage control mode when the load circuit is set to the second operating mode. In accordance with such a construction, it is possible to solve a reduction in utilization efficiency of the power of the electricity supply device 101 with respect to the load circuit 104 as a problem in a period in which no consumed electric current of the load circuit 104 is almost varied.
Further, the load circuit outputs an operating mode signal for notifying in which of the first and second operating modes the loading circuit is operated. In accordance with such a construction, in addition to the effects of the above construction, the operating mode of the load circuit can be reliably known so that control can be more reliably performed and power can be stably supplied to the load circuit.
Further, the electronic apparatus further comprises electric current detecting device in a power supply path from the electricity supply device to the load circuit, and the electric current detecting means judges in which of the first and second operating modes the load circuit is operated on the basis of electric current detecting results, and outputs an operating mode signal for notifying the operated operating mode of the load circuit. In accordance with such a construction, the operating mode of the load circuit can be reliably known so that control can be more reliably performed. Further, power can be stably supplied to the load circuit, and there is also an effect in that a load circuit except for the load circuit able to output the operating mode signal can be adopted.
Further, the electric current detecting device has electric current detecting values at two levels between a first consumed electric current value in the operation of the load circuit in the first operating mode and a second consumed electric current value in the operation of the load circuit in the second operating mode, and the electric current detecting device outputs a signal judged as a switching period of the first and second operating modes by the load circuit as the operating mode signal in a detecting period of the electric current value between the electric current detecting values at the two levels. In accordance with such a construction, in addition to the effects of the above construction, closer control can be performed, and power can be stably supplied to the load circuit.
Further, an electronic apparatus comprises electricity device for supplying first power; a first voltage converting circuit for outputting second power different in voltage from the first power on the basis of the first power; a second voltage converting circuit for outputting third power different in voltage from the first power on the basis of the second power; and a load circuit operated by fourth power based on the second power and the third power; wherein the first voltage converting circuit has high power supply ability in comparison with the second voltage converting circuit; the second voltage converting circuit has high conversion efficiency in comparison with the first voltage converting circuit at a supply time of low power; the load circuit has at least a first operating mode and a second operating mode having a variation of a consumed electric current smaller than that in the first operating mode; and the electronic apparatus has a period for generating the fourth power based on the second power in the first operating mode of the load circuit, and generating the fourth power based on only the third power by stopping an operation of the first voltage converting circuit in the second operating mode of the load circuit. In accordance with such a construction, it is possible to solve a reduction in utilization efficiency of the power of the electricity supply device 101 with respect to the load circuit as a problem in a small period of the consumed electric current of the load circuit 104.